Active noise compensation

ABSTRACT

A method is for controlling a multi-phase electrical ship propulsion motor that is supplied with electric energy via a power converter. The ship propulsion motor is preferably a permanently excited motor with at least three windings. The phase currents flowing in the windings are controlled via the power converter to minimize the body noise emitted by the electrical ship propulsion motor.

This application is the national phase under 35 U.S.C. § 371 of PCTInternational Application No. PCT/DE01/04344 which has an Internationalfiling date of Nov. 19, 2001, which designated the United States ofAmerica and which claims priority on German Patent Application number DE100 58 293.1 filed Nov. 23, 2000, the entire contents of which arehereby incorporated herein by reference.

FIELD OF THE INVENTION

The invention generally relates to a method for controlling a polyphaseelectrical ship propulsion motor which is supplied with electrical powervia a converter. T ship propulsion motor is preferably in the form of amotor with permanent magnet excitation having at least three windings.

BACKGROUND OF THE INVENTION

Polyphase electrical ship propulsion motors, which are fed byconverters, produce low-frequency structure-borne sound which isessentially due to oscillating moments in the motor. Suchstructure-borne sound emission is particularly dangerous for submarines,since low-frequency noise is carried over particularly long distances inwater.

SUMMARY OF THE INVENTION

An object of an embodiment of the invention is to suppress (preferably,as far as possible) structure-borne sound emissions. In particular, itis an object to suppress them from motors in submarines, and also fromthe motors in electric steering propellers, irrespective of whetherthese are used for navy ships or for cruise ships etc.

An object may be achieved in that the phase currents flowing in thewindings of the electrical propulsion motor are controlled via theconverter in order to lessen, preferably minimize, the structure-bornenoise originating from the electrical ship propulsion motor. A controlsystem such as this may, for example, be in the form of vectorialcontrol of the residual direct-current components to produce a totalcurrent of zero. This very considerably reduces the resultantlow-frequency structure-borne sound level from such motors. The acousticsignature, in particular of submarines, but also of navy service ships,can thus be approximated to the acoustic signature of electrical mainpropulsion machines which are not fed via converters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a vector diagram with the residual, very small, resultantdirect-current vector.

FIG. 2 shows an illustration, shown in schematic form, of the influenceof the individual phases with the arrangement of selected sensors.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The control principle can be seen in FIG. 1, wherein FIG. 1 shows avector diagram with the residual, very small, resultant direct-currentvector. The control system is preferably in the form of software,although a hardware implementation is also possible. The signals whichare produced are advantageously transmitted via existing bus systems.

In at least one embodiment of the invention, each individual phase ofthe converter has an associated regulator for suppressing thedirect-current component. The regulator may be a Simatic-S7 regulator.The regulators for the individual phases are linked to one another andform a control system in which the mutual influence between theindividual winding currents is taken into account. In particular, thedirect-current component is suppressed as far as possible. Actual valuesdepicted with the aid of known sensors and calculation methods are usedas the basis of the control system. Acceleration sensors, angle positionsensors etc. are also used as sensors.

FIG. 2 shows an illustration, shown in schematic form, of the influenceof the individual phases with the arrangement of selected sensors.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. A method for controlling a polyphase electrical ship propulsion motorsupplied with the electrical power converter, comprising: detectingphase currents flowing in the windings of an electrical propulsionmotor; determining low frequency structure-borne noise signals fromdetected phase currents; generating residual resultant direct currentvectors as a function of the determined low frequency structure-bornenoise signals to control the residual direct current components toproduce a total current of zero; and controlling DC components of phasecurrents flowing in the windings via the converter such thatnoise-producing current components counteract one another in order tolower the structure-borne noise originating from the electrical shippropulsion motor.
 2. The method as claimed in claim 1, wherein the DCcomponents which occur in the windings are controlled to a total currentof zero.
 3. The method as claimed in claim 2, wherein a control systemworks to keep the low-frequency components of the structure-borne noisethat is produced, small.
 4. The method as claimed in claim 3, whereinthe control system is in the form of a software control system.
 5. Themethod as claimed in claim 3, wherein a control system in the form of asystem with at least one programmable controller is used as the controlsystem.
 6. The method as claimed in claim 5, wherein the noise islowered by configuration of the system with at least one programmablecontroller.
 7. The method as claimed in claim 6, wherein theconfiguration process is carried out with respect to current curveforms, frequency control and pulse formation.
 8. The method as claimedin claim 5, wherein the configuration process is carried out withrespect to current curve forms, frequency control and pulse formation.9. The method as claimed in claim 1, wherein the method is used inunderwater vessels.
 10. The method as claimed in claim 1, wherein themethod is used for motors for electric steering propellers.
 11. Themethod of claim 1, wherein the ship propulsion motor is in the form of amotor with permanent magnet excitation including at least threewindings.
 12. The method as claimed in claim 1, wherein noise-producingcurrent components are controlled such that their noise-producingeffects tend to cancel one another out as far as possible.
 13. Themethod as claimed in claim 12, wherein the DC components which occur inthe windings are controlled to a total current of zero.
 14. The methodas claimed in claim 1, wherein system for the step of controlling is inthe form of a software control system.
 15. The method as claimed inclaim 1, wherein a control system in the form of a system with at leastone programmable controller is used for the step of controlling.
 16. Themethod as claimed in claim 15, wherein the noise is lowered byconfiguration of the system with at least one programmable controller.